We have the same situation. I feed my chicks starter now, however, everyone else can get to it too, and they do sometimes. (but it won't hurt them). I do plan to switch them onto grower here in a couple weeks. Then I just put the regular feeder (that has layer feed) up on an extra cynder block for now, and the babies can't reach it, so the others can still eat it as they please.
As for the hen, she is okay to eat whatever the babies are eating, and there really isn't anyway to keep her from eating it unless you seperate her from the babies.
Good luck